An interesting issue arose today, in reviewing a product. I
thought I'd share the joy.
Consider a garden variety piece of ITE with and appliance
inlet/EMI filter combination and a PE bonding conductor from
an EMI filter terminal to a stud pressed into the chassis.
The area around the stud does not bear the IEC60417, Symbol
5019.
In reviewing the Subject marking requirements in IEC60950-1,
I noted that Subclause 1.7.7.1, first paragraph, contains
the expected statement regarding marking of a PE terminal.
However, Subclause 2.6.4.2, second sentence of the first
paragraph, seems to make additional marking of internal
conductors bonded to chassis unnecessary. (This same
wording was used in IEC60950:1999, Subclause 2.6.4.2, second
sentence of the first paragraph.)
ITE with an IEC60320 appliance inlet provided with the
IEC60417, Symbol 5019, need no further marking of the
end-product. ¿ER? The product complies with 60950-1¡¿?!
Whoa ... I must've had something extra special in my coffee
this morning.
But wait! There's more!
IEC60320-1:1999+A1+A2, Clause 8, indicates that certain
constructions, such as those identified above, do not
require protective earthing terminal marking. Likewise,
Subclause 8.6 makes it plain that appliance inlets intended
for integration into an appliance or equipment does not need
to be marked. (I don't know what later versions might
state.)
In sum:
60950-1 requires marking the PE terminal
60320-1 claims marking the PE terminal is optional, for
certain constructions (nonrewirable, nonreversable)
60950-1 states that the PE terminal's location *is in* the
appliance inlet, if a detachable power supply cord is used
But wait! There's more!
The aforementioned version of IEC60320-1, Subclause 8.4,
allows marking with IEC60417, Symbol 5017 (no circle),
though a note states, "preferably the symbol with a circle
should be used." In IEC60950-1, marking a PE terminal with
Symbol 5017 is naughty.
So, careful selection of components can yield lesser cost
products by not needing to additionally mark an end-product.
Selection of a component that is not marked requires marking
of the appliance inlet in the final application, which
differs from the previous tack of marking the. Selection of
a component that is marked incorrectly could lead to a
noncompliance or, if not noted by a safety agency engineer,
deployment of noncompliant product into the field.
If anyone out there has a copy of the IEC EMI filter
standard, it would be interesting to know the PE terminal
marking requirements of that document.
I've brought this to the attention of a member of TC108
(others subscribe to this list). His comment was, "I don't
like it." Still, TC108 membership should be cognizant of
this and consider it in their deliberations.
Regards,
Peter L. Tarver, PE
ptar...@ieee.org
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